1. Field of the Invention
The present invention relates to devices for conducting immunoassay procedures. More particularly, the invention relates to disposable, pre-packaged devices which are particularly suitable for conducting diagnostic procedures based on immunological reactions using specimens gathered on swabs at remote sites such as physician's offices and homes of users.
2. Description of the Prior Art
Since the important discovery of Milstein and Kohler reported in Nature 256: 495-497, 1975, the development of highly sensitive and specific immunoassay procedures has proceeded at a rapid pace. In fields such as clinical medicine, forensic sciences, environmental quality testing, food quality assurance, drug testing and other related areas, it has become possible to determine the presence and/or amount of trace substances in test samples even when such substances are present in very low concentrations in the order of parts per million, or even less. The development of non-radioactive labels or markers, such as enzyme color formers, has facilitated the use of immunoassay diagnostic procedures outside of laboratory settings and in remote sites such as physician's offices and even the homes of the users. In the physician's office, immunological procedures are useful for providing rapid, simple assays which may be performed while the patient is still in the office so that the diagnosis can be accomplished without delay and treatment instituted during a single visit. Without such simple assays, it has often been necessary for the physician to collect a sample from a patient during a first visit and to have the sample analyzed by a clinical laboratory with the results reported back to the physician by the laboratory at a later time. In the meanwhile, the patient was sent home and was required to return for a second visit with the physician in order to receive appropriate treatment and/or medication. Manifestly, such delay was inefficient and inappropriate and in some cases could even be life threatening.
Home testing has become desirable to facilitate testing by the consumer in the privacy of his or her own home. The results of such testing might, for example, indicate the necessity or lack of necessity of a visit to the physician. Examples of useful tests for the "at home" market include tests for pregnancy, ovulation, streptococcus infection and other infections which are detectable by analysis of body fluids such as urine, saliva, throat fluids, pus, vaginal fluids, blood or other appropriate test samples.
For remote site testing, assuming appropriate sensitivity and specificity can be achieved, there are at least three other requirements for practical assay procedures. The first of these desirable factors is speed in that the assay must be performed in an acceptably short period of time, the shorter the better. Stability is also a desirable feature in that the components of the assay should be stable for an extended period of time without refrigeration or special handling. Finally, from a commercial view point it is desirable that the test be convenient to use and as simple as possible requiring only minimal or no instrumentation and precluding mistakes and poor performance resulting in incorrect interpretations.
One of the difficulties encountered in the development of test devices for remote site testing is the provision of a practical pre-packaged disposed device to facilitate efficient, relatively inexpensive, foolproof test procedures. This, of course, requires a device which is inexpensive to construct, which has a shelf life appropriate to the commercial use of the device, which is protected against contamination during handling, which may be simply and conveniently utilized when the appropriate time arises, and which may conveniently and safely be used by even untrained persons.
The device illustrated in U.S. Pat. No. 4,632,901 addresses some of these problems and is available commercially; however, the device has a number of deficiencies including the fact that it is useful only in connection with urine or other pourable fluid samples. Another device for testing pourable fluid samples is illustrated in the co-pending, commonly owned application of Lennon and Murphy, U.S. patent application Ser. No. 107,240, filed Oct. 13, 1987.
Other prior single test devices are illustrated in United States Letters Patent Nos. 4,366,241 and 4,623,461. However, these devices are of limited application and have excessive complexity.
None of these prior art devices addresses the particularly difficult set of problems that are encountered when a sample is collected on a swab or the like for delivery to the test device, such as is necessary in the case of a strep throat test, for example. Rather, to use prior devices with a test sample collected on a swab, it was generally necessary to utilize techniques involving manual expression of the specimen fluid from the swab to form a pourable liquid test mixture or the streaking of the swab on an agar plate.